Each layer is a write only operation. So if you `RUN some_build.sh` and then `RUN rm junk`, you basically do nothing to reduce the final image size. So you see

Each layer is a write only operation. So if you `RUN some_build.sh` and then `RUN rm junk`, you basically do nothing to reduce the final image size. So you see a lot of like `RUN some_build.sh && rm -rf junk`. There's some overhead with each layer as well.